shinyServer(function(input, output, session) {
  observe({
    # We'll use the input$controller variable multiple times, so save it as x
    # for convenience.
    x <- input$controller
    r_options <- list()
    r_options[[sprintf("option label %d 1", x)]] <- sprintf("option-%d-1", x)
    r_options[[sprintf("option label %d 2", x)]] <- sprintf("option-%d-2", x)
    # Change values for input$inRadio
    updateRadioButtons(session, "inRadio", choices = r_options)
    # Can also set the label and select an item
    updateRadioButtons(session, "inRadio2",
      label = paste("Radio label", x),
      choices = r_options,
      selected = sprintf("option label %d 2", x)
    )
  })
})Run the code above in your browser using DataLab